Field of the Invention
The present invention relates to a robot apparatus that performs an inserting operation of inserting an inserting object piece to an inserting target piece, a controlling method of the robot apparatus, a program and a recording medium.
Description of the Related Art
A compliance control using a force sensor is generally performed when a robot apparatus is used to carry out an operation of assembling pieces together involving contact of the pieces, specifically, an inserting operation of inserting an inserting object piece to an inserting target piece. The compliance control is a control of providing a virtual spring property and viscosity to a robot arm with respect to force (including force and moment of force) applied to a robot hand grasping an inserting object piece to make the robot arm flexible with respect to reaction force. The compliance control allows carrying out the inserting operation by correcting a positioning error of the robot arm, a position error of the inserting target piece and grasping reproducibility of the robot hand. However, if there is a poor fit during the insertion, stronger reaction force is necessary to eliminate this state, and the force may exceed the allowable power of the force sensor. Therefore, eliminating the poor fit only under the compliance control is difficult.
Methods of using vibration to eliminate a poor fit of an inserting object piece during an inserting operation are disclosed in Japanese Patent No. 4793694 and Japanese Patent Application Laid-Open No. H04-322994. In Japanese Patent No. 4793694, when it is judged that there is a poor fit during an inserting operation under force control, a feed-back target value of the force control is periodically changed to provide vibration force to eliminate the poor fit. In Japanese Patent Application Laid-Open No. H04-322994, a vibrator including a cut and a piezoelectric element is attached to a base part of a hand, and vibration of the vibrator applies vibration to the hand to thereby eliminate the poor fit.
However, since the force control is used to provide vibration to the inserting object piece in Japanese Patent No. 4793694, the frequency of the provided vibration is limited by the response frequency of the force control and the eigenvalue of the robot arm, and the poor fit of the inserting object piece may not be eliminated. Meanwhile, the vibrator is used to apply vibration to the inserting target piece in Japanese Patent Application Laid-Open No. H04-322994. However, the entire hand with a large mass is excited by the vibrator in Japanese Patent Application Laid-Open No. H04-322994, and the vibration tends to attenuate. Therefore, the vibration cannot be efficiently provided to the inserting object piece, and the poor fit of the inserting object piece may not be eliminated.
An object of the present invention is to eliminate a poor fit state when an inserting object piece poorly fits to an inserting target piece.